ROCHESTER, N.Y. — Al Palmer has a slim build, an easy smile, and a near-insatiable hunger for human flesh.

Palmer, 27, of Litchfield, Maine, is an industrial-design student at Rochester Institute of Technology. He wears in his headband the IDs of 17 students who had been humans until he tagged them, turning them into zombies.

"I get the biggest kick out of walking up behind someone who's looking all around except behind them," he says as his group prepares to head out into the night. "It gets your heart pumping, that exhilaration."

Welcome to the world of Humans vs. Zombies (HvZ), a tag-like game that is the latest trend in campus entertainment. An HvZ game typically involves hundreds of students and runs 24 hours a day for days on end; dwindling numbers of humans try to fend off and outlast growing legions of zombies.

The rules are fundamentally simple: Zombie tags human, human becomes a zombie. Unlike movie zombies, with shambling walks and undead makeup, zombies in the game just wear headbands to distinguish them from armband-wearing humans. And they are free to sprint.

Humans ward off zombies with Nerf guns or by hitting them with a balled-up sock — a defensive move that stuns the zombie, usually for 15 minutes. The goal is to still be a live human at the end.

A group of students at Goucher College in Towson, Md., is credited with starting the game, which has spread across the USA. Addicted to the first-person shooter video game Splinter Cell, the students wanted to create a live version of it on campus; it turned into tag and then became zombie-fied, says Goucher graduate Brad Sappington, one of the creators.

"It just unfolded like that: 'We like zombies. Let's find a way to make real zombies at college.' It was alcohol-induced, I'm sure."

The Internet has played a big role in the spread of the game. Goucher students created a website (hvzsource.com) that is a repository of information about and rules for the game. And YouTube videos of the game being played at Goucher have found fans at other schools.

Ball State University in Muncie, Ind., hosted its first student-organized HvZ game last fall after one student stumbled across online video footage of the game and brought the idea there, says Jason White, 23, a senior from Indianapolis who is organizing a tournament there this week.

RIT hosted its first HvZ game last fall after Zack Bessler, 21, a computer science major from Lyman, Maine, said he came across information about the game.

"It just sounded like ridiculous amounts of fun," Bessler says. "Does it get any better than zombie-themed tag?"

Choose a spot to play at. Make sure it is a wide space, for you'll probably need to run a lot. If there's a playground structure, you can use some of that too.

Choose the one who is 'it'. They are the zombie.

You all(not the zombie) get a start of 5-10 seconds. That way if you start out in a tight spot you will be able to get a head start without being tagged.

If you get tagged, you are a zombie too. The previous one is still it. That means you are both it. The same applies for others.

When only one person is left in not being a zombie, they win.

The last person alive is the first zombie the next round, so watch out!

Tips

You don't have to walk like a zombie.

The more people the more fun.

Make sure you know who is a zombie at all times. Try staying with a friend who you know is not a zombie so that you don't get caught.

You could play a variation with a base if you like.

Other variations of zombie tag include randomly picking the zombie by way of handing out one marked piece of paper among many. Tagging rules that require both hands and touching the forehead are also fun.